Optical glass, precision press-molding preform, process for producing the preform, optical element and process for producing the optical element

摘要

Provided are optical glasses having a refractive index (nd) of over 1.82 but not more than 1.86 and an Abbe's number (νd) of 30 to 39.5 and having the property of low-temperature softening that permits precision press-molding, one is an optical glass comprising B₂O₃, La₂O₅, Gd₂O₃ and ZnO as essential components, comprising Li₂O and SiO₂ as optional components, provided that the content of SiO₂ is less than 2% by weight when Li₂O is contained, having a refractive index (nd) of over 1.82 but not more than 1.86 and an Abbe's number (νd) of 30 to 39.5 and having a glass transition temperature (Tg) of 630° C. or lower, and the other is an optical glass comprising, by % by weight, 14 to 30% of B₂O₃, 10 to 40% of La₂O₃, 1 to 30% of Gd₂O₃ and 6 to 26% of ZnO as essential components, and comprising, as optional components, predetermined amounts of WO₃, Ta₂O₅, Nb₂O₅, TiO₂, SiO₂, Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO, Y₂O₃, Yb₂O₃, ZrO₂, Bi₂O₃ and Sb₂O₃ and having a refractive index (nd) of over 1.82 but not more than 1.86, an Abbe's number (νd) of 30 to 39.5 and a glass transition temperature (Tg) of 630° C. or lower.